While a resident in Surgery at the Massachusetts General Hospital in the early 1980s, he cared for several hundred-year-old surgical patients and reviewed the records of other elderly patients. All six survived operation and enjoyed life for one or two years, one even taking an around-the-world cruise and returning to lecture at a local college.

Dr. Katlic published his results in 1985 in the Journal of the American Medical Association. With his interest sparked, he went on to publish five textbooks of geriatric surgery. He also speaks frequently at medical schools and hospitals.